Tutorial: Getting Started with the D-lang Native Core

Table of Contents

Prerequisites
Step 1: Compiling the Native Core
Step 2: Testing Metadata Probing
Step 3: Simulating a Piped Mixdown

This tutorial guides you through the process of compiling, running, and validating the D-lang native supervisor core (multimux-core) on your system.

Prerequisites

Before you begin, ensure you have the following installed on your machine:

* [ ] DMD Compiler: The reference compiler for the D programming language.
* [ ] DUB Package Manager: The standard package and build manager for D (usually bundled with DMD).
* [ ] FFmpeg and FFprobe: Native command-line executables registered in your system’s environment PATH.

Step 1: Compiling the Native Core

To compile the multimux-core binary:

Open your terminal or PowerShell console.
Navigate to the core directory inside the project workspace:
```
cd Z:\code\github.com\amdphreak\multimux\core
```
Execute the release build command using DUB:
```
dub build --compiler=dmd --build=release
```
DUB will automatically compile the source files in source/app.d and output a compiled binary:
- On Windows: core/multimux-core.exe
- On macOS/Linux: core/multimux-core

Step 2: Testing Metadata Probing

To verify that the core communicates successfully with ffprobe:

Run the core binary with the probe command, passing the absolute path to any multi-track video file:
```
.\multimux-core.exe probe "C:\Users\rjamd\Videos\my-game-recording.mkv"
```

The D-lang core will execute ffprobe in a piped subprocess, parse the output, and print a clean, structured JSON payload directly to the standard output:

{
  "streams": [
    { "index": 0, "codec_name": "h264", "codec_type": "video", "width": 1920, "height": 1080 },
    { "index": 1, "codec_name": "aac", "codec_type": "audio", "channels": 2, "tags": { "title": "Game Audio" } },
    { "index": 2, "codec_name": "aac", "codec_type": "audio", "channels": 2, "tags": { "title": "Microphone" } }
  ]
}

Step 3: Simulating a Piped Mixdown

To test the audio muxing supervisor directly from the command line:

Create a raw JSON options payload that specifies the source, destination, target codecs, and track multipliers:

{
  "filePath": "C:\\Users\\rjamd\\Videos\\input.mkv",
  "outputPath": "C:\\Users\\rjamd\\Videos\\output.mkv",
  "audioCodec": "aac",
  "audioBitrate": "192k",
  "duration": 60.0,
  "selectedStreams": [
    { "relativeIndex": 0, "volume": 1.0 },
    { "relativeIndex": 1, "volume": 1.5 }
  ]
}

Feed this JSON string directly as an argument to the mux command:
```
.\multimux-core.exe mux "{\"filePath\":\"input.mkv\", ...}"
```

Watch the real-time, typed JSON events printed to stdout:

{"type": "log", "message": "Spawning FFmpeg..."}
{"type": "progress", "percent": 12.40}
{"type": "progress", "percent": 24.80}
{"type": "progress", "percent": 100.0, "message": "Success"}
{"type": "done"}

These are the clean, structured messages that the Electron renderer consumes to render the CRT console without lagging the interface.